Airbag module for motor vehicles

ABSTRACT

The invention relates to an airbag module for motor vehicles comprising a housing for an inflatable airbag and a gas generator which is connected to a base element fixed to the module in the assembled state, with the gas generator and the base element being combined to form an assembly serving as a vibration absorber and being unreleasably connected to one another by at least one elastic and/or vibration damping coupling element via which the gas generator is supported over its area at the base element.

[0001] The invention relates to an airbag module for motor vehicleshaving a housing for an inflatable airbag and a gas generator.

[0002] Such airbag modules serve to receive the airbag in the foldedstate and to inflate it by means of the gas generator in the case of acrash. The airbag modules are installed in the vehicle as a unit. It isa problem, in particular with driver airbags to be installed at thesteering wheel, that vibrations which occur during the operation of thevehicle can be transmitted to the steering wheel unit and thus to theairbag module.

[0003] It is the underlying problem (object) of the invention to providean airbag module of the kind initially mentioned which has as simple aconstruction as possible and which is not impaired by vibrations whichoccur and which can be used in particular as a driver airbag which canbe integrated into a steering wheel unit.

[0004] This object is satisfied by the features of claim 1 and inparticular by the gas generator being connected to a base element fixedto the module in the assembled state, with the gas generator and thebase element being combined to form an assembly serving as a vibrationabsorber and being unreleasably connected to one another by at least oneelastic and/or vibration damping coupling element via which the gasgenerator is supported over its area at the base element.

[0005] In accordance with the invention, the gas generator, which has acomparatively large mass, is used as a vibration damper. It is ofparticular advantage that the gas generator and the base element, whichform the vibration absorber assembly together with the coupling elementand which are unreleasably connected to one another by the couplingelement, are used as a unit and can be commonly integrated into themodule when the airbag module is assembled. The manufacture of theairbag module is made substantially simpler in this way. In particular,additional measures to hold the unit of gas generator, base element andcoupling element together are superfluous due to the unreleasability ofthe connection made between the gas generator and the base element bythe coupling element. The areal support of the gas generator means thatthe coupling element serves as an elastic and/or vibration damping basecomponent, i.e. the base element and the coupling element jointly form abase assembly for the gas generator which is able to damp or decreasevibrations. Furthermore, the stress of the coupling element with respectto a coupling element formed, for example, as an elastic suspension canbe reduced by the coupling element serving as a support for the gasgenerator. Damage to the coupling element caused in particular bymaterial fatigue can be prevented in this way in accordance with theinvention. It is moreover of advantage that the installation procedureand the installation position of the assembly with respect to a fixedtying of the gas generator practically do not need to be changed due tothe invention.

[0006] It is particularly preferred if the base element, the couplingelement and the gas generator at least regionally form a sandwich-likeassembly.

[0007] In a further practical embodiment of the invention, it isprovided that the coupling element is vulcanized both to the gasgenerator and to the base element.

[0008] This connecting of the coupling element to the gas generator andto the base element, which is free of securing means, but which isnevertheless stable and secure, allows a simple manufacture and handlingof the vibration absorber. Moreover, in this way, a gas-tight connectionof the gas generator to the base element and thus to the airbag modulecan be simply ensured with the coupling element.

[0009] The coupling element consists for example of rubber or arubber-like material.

[0010] In accordance with the invention, other materials can generallybe used for the coupling element and/or in particular different ways ofsecuring the coupling element to the gas generator and to the baseelement can be used.

[0011] It is particularly preferred for the coupling element to have ahigher stiffness parallel to a longitudinal module axis thanperpendicular to the longitudinal module axis. This embodiment is inparticular advantageous for airbag systems which can be integrated intosteering wheel units.

[0012] In accordance with a further preferred embodiment of theinvention, the coupling element has a closed peripheral contour and isin particular of an annular shape.

[0013] The coupling element can simultaneously carry out a plurality offunctions by this embodiment in that it, on the one hand, provides anelastic connection of the gas generator to the base element and, on theother hand, ensures the gas-tightness between the gas generator and thebase element.

[0014] In a preferred variant of the invention, the coupling element canhave a wall thickness which varies in the peripheral direction. Aparticularly preferred embodiment provides that the coupling element hascontact regions with a relatively large wall thickness distributed inthe peripheral direction and sealing regions with a relatively smallwall thickness between the contact regions, with the contact regions,which serve as elastic coupling bases and, for example, have an at leastapproximately circular or semi-circular contact area, providing asufficient stability and stiffness of the connection, while the wallregions extending between these contact bases substantially carry out asealing function. The coupling element and thus the absorber assemblycan be directly matched to the respective demands by a correspondingdimensioning, in particular of the contact regions.

[0015] In a particularly preferred embodiment of the invention, thecoupling element is formed as a radial vibration limiter for the gasgenerator, with the coupling element not only serving for the support ofthe gas generator at the base element, but simultaneously fulfilling avibration limitation function in the radial direction. Additionalmeasures such as separate vibration limiters are hereby not necessary.The manufacture of the airbag module can be substantially simplified inthis manner since care only has to be taken for the connection of thecoupling element to the gas generator and to the base element and inthis manner care is already taken for a secure support of the gasgenerator at the base element and a limitation of radial vibrations ofthe gas generator, or vibrations of the gas generator perpendicular to alongitudinal module axis, is also ensured.

[0016] It is preferred for the coupling element and the gas generator tomutually overlap in the axial direction—with respect to a longitudinalmodule axis. In this respect, the gas generator can contact the couplingelement directly in an areal manner in the radial direction, withpreferably a radially outer surface of the gas generator being fixedlyconnected, in particular by vulcanization, to the coupling element or toa radially outwardly lying section of the coupling element.

[0017] In accordance with a particularly preferred practical embodiment,the gas generator is inserted into the coupling element and issurrounded at least regionally by the coupling element. A particularlystable connection is hereby realized between the gas generator and thecoupling element.

[0018] It is particularly preferred for the coupling element to beformed in step shape at least regionally for the simultaneous axial andradial support of the gas generator.

[0019] The coupling element can have a peripheral support step for thegas generator at its radial inner side.

[0020] The gas generator can be placed onto a step-shaped section or asupport step of the coupling element and can simultaneously be fixedlyconnected to the coupling element, in particular by vulcanization, via alower and a radially outer or inner surface.

[0021] The coupling element preferably has two annular sections radiallyoffset with respect to one another in order to form a support step forthe gas generator.

[0022] It is further proposed for the coupling element to havereinforcement regions distributed in the circumferential direction inwhich the wall thickness of the coupling element is enlarged incomparison with regions disposed between the reinforcement regions inparticular in the region of an upper and/or of a lower annular section.

[0023] The gas generator can have a collar for the support of thecoupling element which is preferably formed at least approximately in aU shape in cross-section.

[0024] It is preferred in this respect for the collar to be arranged ina manner radially outwardly offset and in particular to merge via astep-shaped transition section into a side wall of the gas generatorwhich preferably extends axially.

[0025] In accordance with a further preferred embodiment of theinvention, at least one preferably separate vibration limiter isadditionally provided for the gas generator and is preferably made of anelastic material. The vibration limiter can have a greater stiffnessthan the coupling element at least perpendicular to a longitudinalmodule axis. A plurality of such vibration limiters are preferablyprovided.

[0026] Relative movements between the gas generator and the baseelement, which the coupling element permits due to its design, can belimited by the vibration limiter(s). The coupling element can thereby beoptimized with respect to its vibration damping function without havingto meet any certain marginal conditions with respect to protection dueto possible movements of the gas generator. In particular, such relativemovements can be suppressed by the additional vibration limiters where,without this preferred embodiment of the invention, the danger wouldarise that the coupling element would be released from the gas generatoror from the base element or that the coupling element would tear.

[0027] The vibration limiters are preferably formed with a pin shape andpreferably extend approximately parallel to a longitudinal module axisof the gas generator.

[0028] It is furthermore preferred for the vibration limiters each to befixed at the base element with one end and to engage into a recess ofthe gas generator with another.

[0029] The invention moreover relates to a method for the manufacture ofan airbag module for motor vehicles comprising a housing for aninflatable airbag and a gas generator in which an assembly serving as avibration absorber is manufactured by a coupling element beingunreleasably connected both to the gas generator and to a base elementand by the assembly being integrated into the airbag module as a unit.

[0030] Further improved embodiments of the invention are also given inthe dependent claims, the description and the drawing.

[0031] The invention is described in the following by way of examplewith reference to the drawing, in which are shown:

[0032]FIGS. 1a-1 edifferent views of a vibration absorber of an airbagmodule in accordance with an embodiment of the invention; and

[0033]FIGS. 2a-2 f views in accordance with FIG. 1a-1 e of a furtherembodiment of the invention, with FIG. 2f corresponding to FIG. 2c andshowing additional components of the airbag module;

[0034]FIG. 3 a sectioned side view of a vibration absorber of an airbagmodule in accordance with a further embodiment of the invention; and

[0035]FIG. 4 a perspective view of the vibration absorber of FIG. 3.

[0036]FIGS. 1a-1 e show an embodiment of a vibration absorber whichcomprises a gas generator 15, a base element 17, a coupling element 19and vibration dampers 25. This unit forms, together with furthercomponents (not shown), an airbag module which can be integrated into asteering wheel unit of a motor vehicle. The design of the airbag modulewill be looked at in more detail in the explanation of a furtherembodiment of the invention.

[0037] The gas generator 15 comprises a circular cylindrical outer part33 with straight walls, which extend parallel to the longitudinal axisof the airbag module, and with a radially projecting collar 29. A gasgenerator unit 35 is inserted into the outer part 33 and discharges gasafter triggering in the event of an accident. Said gas flows throughopenings formed in the cylinder wall of the outer part 33 and inflatesthe folded airbag.

[0038] The plate shaped base element 17 provided with a central opening31 is unreleasably connected to the collar 29 of the outer part 33 viaan annular coupling element 19 which is vulcanized on the one hand tothe marginal region of the base plate 17 bounding the aperture 31 and onthe other hand to the lower side of the collar 29 of the gas generator15. The coupling element 19 consists, for example, of rubber or arubber-like material, with, however, other elastic and/or vibrationdamping materials also being able to be used which are connected in asuitable manner to the gas generator 15 and the base element 17.

[0039] The wall thickness of the coupling ring 19 varies over itsperiphery and comprises contact regions 21 of comparatively large wallthickness, between which sealing regions 23 with comparatively smallwall thickness extend. The outer edge of the collar 29 follows the outercontour of the coupling ring 19 to the extent that tab-like protrusions30 are provided for the connection of the contact bases 21 having anapproximately semi-circular contact surface and with which the gasgenerator 15 contacts the coupling element 19.

[0040] Two tabs 30 of the generator collar 29 diametrically opposed toone another are provided with a circular recess 27 into which in eachcase one pin-shaped vibration limiter 25 engages which is made of anelastic material and in particular of plastic and which is fixed, forexample latched or clipsed, to the base element 17 with its end opposingthe engagement end.

[0041] The limit pins 25 are designed such that they have a greaterstiffness than the coupling ring 19.

[0042] Openings 37 in the base plate 17 serve the securing of the baseplate 17 to a foundation plate of the airbag module.

[0043] While it can be seen in particular from FIG. 1b that the limitpins 25, which taper towards the top, protrude through the tab openings,FIG. 1c shows in particular the generator unit 35 inserted into theouter part 33, which is also called a generator flange. The outer part33 and the generator unit 35 are welded together. The design of thegenerator unit 35, which can generally be of any form with respect tothe invention, is not looked at in any further detail.

[0044] While FIG. 1c shows a section along a plane extending through thetwo limit pins 25, a section along the line B-B of FIG. 1d is shown inFIG. 1e. In particular the different wall thicknesses in the contactregions 21 on the one hand and the sealing regions 23 on the other handcan be seen from FIG. 1e.

[0045] The elastic coupling ring 19 has a comparatively high stiffnessparallel to the longitudinal module axis, i.e. parallel to the straightside wall 34 of the outer part, and a relatively low stiffnessperpendicular to the longitudinal module axis. The gas generator 15 canthus oscillate ideally with respect to its vibration absorption functionrelative to the base element 17 fixed to the module during the operationof the vehicle when the airbag module is integrated into the steeringwheel unit. Lateral movements of the gas generator 15 perpendicular tothe module axis are limited by the comparatively stiff vibration limiter25.

[0046] The resonance properties of the system capable of vibration canbe set directly in dependence on the respective circumstances anddemands by a corresponding selection of the material and, for example,of the composition of the rubber mixture of the coupling element 19.

[0047] A substantial advantage of the connection in accordance with theinvention of the gas generator 15 to the base element 17 is that, incomparison to a rigid connection between the gas generator and the baseelement, no disadvantageous compromises have to be made. In particular,neither the installation procedure nor the installation position of thevibration absorber assembly in accordance with the invention aresubstantially changed with respect to a rigid gas generator unit.

[0048] The variant of the invention shown in FIG. 2a-2 f corresponds tothe embodiment of FIGS. 1a-1 e with the difference that the outer part33 of the gas generator 15 has no straight side wall 34, but merger intothe collar 29 from a straight side wall section via a radially extendedside wall section 36 which has an approximate step shape. The inventioncan consequently be used without problem with variously designed gasgenerators 15 and/or outer parts 33 of gas generators 15.

[0049]FIG. 2f additionally shows, in a representation corresponding toFIG. 2c, a diffuser cap 16 surrounding the gas generator 15 at a spacingwhose wall is provided with gas throughflow orifices. A gas inlet spaceis present between the outer part 33 of the gas generator 15 and thediffuser cap 16, into which gas generated by the generator unit 35 flowsbefore it enters the airbag 13.

[0050] The folded airbag 13, which is only schematically indicated inFIG. 2f and which is anchored to the airbag module in a suitable manner,surrounds the diffuser cap 16 and is located inside an outer cover 12 ofthe airbag module which is a component of the module housing 11.

[0051] The cover 12 or the module housing 11 and a foundation plate 14,at which the base element 17, the diffuser cap 16 and/or the cover 12are secured in a suitable manner, optionally via additional modulecomponents, are only indicated schematically in FIG. 2f by chain-dottedlines.

[0052]FIGS. 3 and 4 show a particularly preferred embodiment of avibration absorber which can be manufactured in a particularly simplemanner and which nevertheless simultaneously provides a reliable supportof the gas generator 15 at the base element 17 and a limitation ofradial vibrations of the gas generator 15.

[0053] The embodiment in accordance with FIGS. 3 and 4 differs from theembodiments explained above by the design of the collar 29 of the gasgenerator 15 and by the design of the annular coupling element 19.

[0054] The initially straight side wall 34 of the outer part 33 of thegas generator 15 formed as one piece merges via a step-shaped transitionsection 39 into a free end of the collar 29 which is U shaped incross-section and which is bent outwardly and upwardly. Thecircumferential collar 29 is in this manner radially outwardly offsetwith respect to the side wall 34 by means of the transition section 39.The collar 29 is formed by a deep-drawing process in the manufacture ofthe outer part 33.

[0055] The coupling ring 19 vulcanized onto the base element 17 consistsof a lower annular section 43 and an upper annular section 41. The lowerannular section 43 is offset radially inwardly with respect to the upperannular section 41, whereby a support step is present for the U shapedcollar end of the gas generator 15 at the radial inside of the couplingring 19.

[0056] The coupling ring 19 is molded at its upper annular section 41and in the region of the support step to the radially outer side walland to the base section of the U shaped collar end and is fixedlyconnected by vulcanization to the collar 29. The gas generator 15 isconsequently set with its collar 29 into the coupling ring 19 and ontoits support step such that the gas generator 15 is supported at the baseelement 11 via its collar 29 and via the coupling ring 19 and issurrounded over its whole periphery in the region of the radially outerside wall of the collar 29 by the upper annular section 41 of thecoupling ring 19. In this way, the coupling ring 19 acts against radialvibrations of the gas generator, in particular via the upper annularsection 41, without putting the connection of the collar 29 to thecoupling ring 19 at risk.

[0057] The wall thickness of the coupling ring 19 varies over itsperiphery. As shown in particular by FIG. 4, reinforcement regions 45are distributed over the periphery of the coupling ring 19 and the wallthickness of the coupling ring 19 is enlarged in these with respect tointermediate regions in which the lower annular section 43 forms sealingregions 23. The reinforcements 45 form contact bases 21 for the collar29 of the gas generator 15 in the region of the lower annular section43.

[0058] An enlargement of the wall thickness with respect to theintermediate regions by the reinforcement regions 45 also takes place inthe region of the upper annular sections 41—in comparison with the lowerannular section 43 via a smaller angular region. In this way, thecoupling element 19 is given increased stiffness not only in the regionof the lower annular section 43, but also in the region of the upperannular section 41.

[0059] The enlargement of the wall thickness of the coupling ring 19 bythe reinforcements 45 is effected exclusively by a radial outwardexpansion. The insides of the coupling element 19 are free of recessesand elevations.

[0060] The reinforcements 45 which are formed in column-like orpillar-like manner, which grow radially outwardly from the annularsections 41, 43, which are mutually offset radially, and which areprovided with contact regions 21 which are broadened in the peripheraldirection, have a straight outer surface which extends parallel to theaxially extending side wall 34.

[0061] A reinforcement by radial expansion can alternatively be omittedin the region of the upper annular section 41 which then has a constantwall thickness over the whole periphery.

[0062] The upper annular section 41 closes at its edge flush with theradially outer side wall of the collar 29 of the gas generator 15 whichhas a U shape in cross-section.

What is claimed is:
 1. An airbag module for motor vehicles having ahousing for an inflatable airbag and a gas generator which is connectedto a base element fixed to the module in the assembled state, whereinthe gas generator and the base element are combined to form an assemblyserving as a vibration absorber and are unreleasably connected to oneanother by at least one elastic and/or vibration damping couplingelement via which the gas generator is supported over its area at thebase element.
 2. An airbag module in accordance with claim 1,characterized in that the coupling element is vulcanized both to the gasgenerator and the base element.
 3. An airbag module in accordance withclaim 1 characterized in that the coupling element comprises one or moreof rubber or a rubber-like material.
 4. An airbag module in accordancewith claim 1 characterized in that the coupling element has a higherstiffness parallel to a longitudinal module axis than perpendicular tothe longitudinal module axis.
 5. An airbag module in accordance withclaim 1 characterized in that the coupling element has a closedperipheral contour.
 6. An airbag module in accordance with claim 1characterized in that the coupling element has an annular shape.
 7. Anairbag module in accordance with claim 1 characterized in that thecoupling element has a wall thickness varying in the peripheraldirection.
 8. An airbag module in accordance with claim 1 characterizedin that the coupling element has contact regions distributed in theperipheral direction with a large wall thickness and preferably at leastan approximately circular or semi-circular contact area and sealingregions with relatively small wall thickness between the contactregions.
 9. An airbag module in accordance with claim 1 characterized inthat the coupling element is formed as a radial vibration limiter forthe gas generator.
 10. An airbag module in accordance with claim 1characterized in that the coupling element and the gas generatormutually overlap in the axial direction with respect to a longitudinalmodule axis.
 11. An airbag module in accordance with claim 1characterized in that the gas generator contacts the coupling elementdirectly in an areal manner in the radial direction.
 12. An airbagmodule in accordance with claim 1 characterized in that the gasgenerator is inserted into the coupling element and is surrounded atleast regionally, in particular in the region of a collar by thecoupling element.
 13. An airbag module in accordance with claim 1characterized in that the coupling element is formed in step shape atleast regionally for the simultaneous axial and radial support of thegas generator.
 14. An airbag module in accordance with claim 1characterized in that the coupling element has a peripheral support stepfor the gas generator and its radial inner side.
 15. An airbag module inaccordance with claim 1 characterized in that the coupling element hastwo annular sections radially offset with respect to one another to forma support step for the gas generator.
 16. An airbag module in accordancewith claim 1 characterized in that the coupling element hasreinforcement regions distributed in the circumferential direction inwhich the wall thickness of the coupling element is enlarged incomparison with regions disposed between the reinforcement regions inparticular in the region of an upper and/or of a lower annular section.17. An airbag module in accordance with claim 1 characterized in thatthe gas generator has a collar for support at the coupling element whichis preferably formed at least approximately in a U-shape incross-section.
 18. An airbag module in accordance with claim 17characterized in that the collar is arranged in a manner radiallyoutwardly offset and merges in particular via a step-shaped transitionsection into a side wall of the gas generator which preferably extendsaxially.
 19. An airbag module in accordance with claim 1 characterizedin that the gas generator has a hat or cap like outer contour and has acollar which is radially projecting or protruding connection to thecoupling element.
 20. An airbag module in accordance with claim 1characterized in that the base element is formed in a plate shape andhas an opening with the coupling element being connected to its boundaryregion.
 21. A method for the manufacture of an airbag module for motorvehicles having a housing for an inflatable airbag and a gas generator,in which an assembly is manufactured which serves as a vibratorabsorber, by a coupling element being unreleasably connected both to thegenerator and to a base element and by the assembly being integratedinto the airbag module as a unit.
 22. A method in accordance with claim20, characterized in that the coupling element is connected to an outerpart in particular with a cap or hat shape, of the gas generator andsubsequently a generator unit is inserted into the outer part and inparticular welded to the outer part.